feat(delegation): uncap max_spawn_depth (floor 1, no ceiling) (#39772)

* fix: respect disabled auto-compaction on context overflow

Port from anomalyco/opencode#30749.

When compression.enabled is false, NO automatic compaction trigger may
fire. The proactive token-threshold paths (preflight + post-response
should_compress gate) already honoured the setting, but the three
provider-overflow recovery paths in the agent loop — long-context-tier
429, 413 payload-too-large, and context-overflow — called
_compress_context() unconditionally, silently compressing and rotating
the session against the user's explicit choice.

Add a single guard at the top of the overflow-recovery dispatch: when
compression is disabled and the error is one of those three overflow
classes, surface a terminal error (compaction_disabled: True) telling the
user to /compress manually, /new, switch to a larger-context model, or
reduce attachments. Manual /compress (force=True) is unaffected — it never
enters this loop.

Tests: new TestOverflowWithCompactionDisabled (413 + 400 overflow don't
compress when disabled; control case still compresses when enabled).
Existing overflow-recovery tests updated to enable compaction explicitly
(they verify the recovery fires); fixture defaults flipped to True to
match production (compression.enabled defaults to True).

* feat(delegation): uncap max_spawn_depth to match max_concurrent_children

Removed the hard ceiling of 3 on delegation.max_spawn_depth. Depth now has
a floor of 1 and no upper limit, mirroring max_concurrent_children. Cost
(each level multiplies API spend) is the practical limiter, not a constant.

- delegate_tool.py: drop _MAX_SPAWN_DEPTH_CAP, _get_max_spawn_depth() floors
  at 1 instead of clamping to [1,3]; depth-limit error string reworded
- config.py / cli-config.yaml.example: doc comments say floor 1, no ceiling
- docs (configuration, delegation, delegation-patterns): range 1-3 -> >=1
- tests: convert clamp-above-3 change-detector into a no-ceiling invariant,
  drop the _MAX_SPAWN_DEPTH_CAP==3 snapshot assert, fix warning-text assert

website/docs/user-guide/features/delegation.md

@@ -214,7 +214,7 @@ delegate_task(
 ```
 
 - `role="leaf"` (default): child cannot delegate further — identical to the flat-delegation behavior.
-- `role="orchestrator"`: child retains the `delegation` toolset. Gated by `delegation.max_spawn_depth` (default **1** = flat, so `role="orchestrator"` is a no-op at defaults). Raise `max_spawn_depth` to 2 to allow orchestrator children to spawn leaf grandchildren; 3 for three levels (cap).
+- `role="orchestrator"`: child retains the `delegation` toolset. Gated by `delegation.max_spawn_depth` (default **1** = flat, so `role="orchestrator"` is a no-op at defaults). Raise `max_spawn_depth` to 2 to allow orchestrator children to spawn leaf grandchildren; 3+ for deeper trees. There is no upper ceiling — cost is the practical limit.
 - `delegation.orchestrator_enabled: false`: global kill switch that forces every child to `leaf` regardless of the `role` parameter.
 
 **Cost warning:** With `max_spawn_depth: 3` and `max_concurrent_children: 3`, the tree can reach 3×3×3 = 27 concurrent leaf agents. Each extra level multiplies spend — raise `max_spawn_depth` intentionally.
@@ -264,7 +264,7 @@ For **durable long-running work** that must survive interrupts or outlive the cu
 delegation:
   max_iterations: 50                        # Max turns per child (default: 50)
   # max_concurrent_children: 3              # Parallel children per batch (default: 3)
-  # max_spawn_depth: 1                      # Tree depth (1-3, default 1 = flat). Raise to 2 to allow orchestrator children to spawn leaves; 3 for three levels.
+  # max_spawn_depth: 1                      # Tree depth (floor 1, no ceiling, default 1 = flat). Raise to 2 to allow orchestrator children to spawn leaves; 3+ for deeper trees.
   # orchestrator_enabled: true              # Disable to force all children to leaf role.
   model: "google/gemini-3-flash-preview"             # Optional provider/model override
   provider: "openrouter"                             # Optional built-in provider